PROPAGATING SPREADING IN BACK-ARC ENVIRON MENT - FIRST RESULTS OF THEPROFETI CRUISE (NORTH FIJI BASIN, SW PACIFIC)

Sampling was conducted as part of the ProFeTi cruise of RV Ails in the middle of the North Fiji Basin along the NS spreading segment, which has been propagating northward inside the N15 segment for at least 1 M a. Despite its back-are geodynamic position, no geochemical signature of a subduction zone is noticeable. The studied sample set shows that the magma reservoir of this propagating segment evolves towards a ther mal and geochemical equilibrium, which is disturbed by the following p rocesses: 1) the influence of the remoteness of the propagator tip fro m the magmatic feed zones focused under the segment centre, 2) the per iodic input of early magmas evolving as the propagator matures, and 3) the cold-edge effect of the N15 crust into which the NS segment propa gates.